The invention relates to the improvement of dirt separating apparatuses, in particular, a dirt removal system for use in a textile machine such as in the blowroom or in the card of a spinning mill.
It is current practice to provide devices with xe2x80x9csucked-off knivesxe2x80x9d both on the cylinder as well as revolving flat and fixed flat cards. These devices are capable of removing dirt particles from the processed material, whereas the fibers are further conveyed with the clothing of the cylinder. Casing segments suitable for this purpose have been described in EP-A-431 482 and in EP-A-366 918. A new arrangement for this purpose has been shown in our EP Application No. 978 106 95.3 which was published on Jun. 17, 1998 under the no. EP-A-848 091.
The attachment of knives to casing segments is also shown in U.S. Pat. No. 4,314,387 and 5,530,994, with the latter providing the introduction of an air stream between a segment and an element attached thereto. Similar air streams have been explained in EP-A-366 692 and EP-A-338 802, whereas EP-A-387 908 stresses the relevance of the air household for the cleaning effect. In all of these cases, the introduction of an air stream is seemingly only designed to improve the separation of dirt, with air turbulence being taken into account or even being desired. They also only deal with the zone upstream of the knife as seen in the direction of the fiber conveyance. CH-B-668 085 also deals with the design of a dirt separating apparatus. The knife and the vacuum chamber are to be provided with an integral arrangement, with the distance between the vacuum chamber and the knife blade to the cylinder being adjustable.
CH-B-668 085 shows in FIG. 2 a solution which is provided with a separating edge on a xe2x80x9cknife blade.xe2x80x9d No statements are made in CH-B-668 085 about the air streams in the working gap between the blade and the cylinder. In an alternative embodiment (FIG. 4) which seems to be equivalent to the embodiment according to FIG. 2, the wall element comprising the separating edge is provided with a curvature which leads to a considerable enlargement of the working gap downstream of the separating edge.
The known systems are used not only for dirt separating devices in the carding machine, but also at other locations in the spinning mill, e.g., in cleaning machines (e.g., flock cleaners) which are provided with separating knives (e.g., according to the first figure of DE-A-44 41 254).
According to EP-A-810 309, a cleaning step is also provided for in the tuft feeder chute of the carding machine. EP-A-894 878 shows a suitable arrangement of a separating edge with a discharge means assigned to the edge.
The state of the art has thus been explained on the basis of xe2x80x9cknivesxe2x80x9d (which are also known as xe2x80x9cbladesxe2x80x9d), with a xe2x80x9cknifexe2x80x9d usually comprising a blade which is adjustable with respect to a rotating roller (e.g., card cylinder). It is also known to exercise such a function by an edge (also known as xe2x80x9cseparatingxe2x80x9d edge), with the edge being formed on an element which is not necessarily designed as an adjustable xe2x80x9cknife.xe2x80x9d The invention can also be applied in such arrangements. In order to avoid cumbersome repetitions in the description, reference will be made hereinafter to an edge, with this term comprising the special form of xe2x80x9cknifexe2x80x9d and xe2x80x9cblade.xe2x80x9d
The invention according to EP-A-848 091 (the xe2x80x9cprior inventionxe2x80x9d) is based on the finding that the air streams play an important role not only for the separation of dirt, but also in connection with the formation of neps. In connection with the latter, the production of turbulence is not desirable. Moreover, the region downstream of the edge is as important as the region upstream of the edge. These findings not only apply to dirt separating devices in the carding machine, but also to other locations within the spinning mill such as cleaning machines that are provided with separating edges. It is the object of the EP-A-848 091 invention to improve the air household downstream of the edge. The formation of neps in fiber-processing machines that is caused by air turbulences can be reduced. It is also possible to achieve an improvement in the separation of dirt per se.
The prior invention provides a fiber-processing machine with a separating edge. Both fibers as well as air are guided past the edge in a substantially predetermined direction of conveyance, and dirt particles are discharged in a selective manner by means of the edge from the stream of air and fibers. The invention is characterized in that at least one measure has been taken in order to influence the air streams in the zone downstream of the knife. The measure can be made in such a way that air turbulences downstream (in the conveying direction) of the edge are limited or even eliminated (to the highest possible extent). In other words, the highest possible laminary flow configuration is to be produced or maintained downstream of the edge. Alternatively, or additionally, the measure can be made in such a way that the air separated by the edge can be discharged substantially without any recirculation.
The measure preferably includes that air discharged by the edge is replaced at least partly by newly introduced air. The newly introduced air flows appropriately into the zone adjacent to the edge, e.g., within a distance of approx. 50 mm downstream of the edge and preferably within a distance of less than 20 mm. In one solution, the newly introduced air flows right behind the edge into the stream of air and fibers. The arrangement according to EP-A-848 091 can be provided in such a way that the effective cross section of the working gap downstream of the edge is provided with an extension. It is not possible to define the degree of extension in advance, e.g., when the position of the edge can be adjusted in the radial direction with respect to the cylinder.
According to the prior invention, means are therefore provided in order to allow the air to flow into the space downstream of the edge. The means can be arranged in such a way that air is allowed to flow in substantially over the entire working width, preferably as evenly as possible over the entire working width. The edge is preferably formed on an element which is suspended in the casing of the cylinder. The casing should be arranged in such a way that the production of the required air stream is enabled.
Preferably, the arrangement is self-adjusting concerning the incoming air quantity, meaning (for example) that it is not necessary to work with blower air. When the free cross section for the flow is adequately dimensioned for the air supply, the required air stream will rise as a result of the negative pressure in the space downstream of the edge.
EP-A-848 091 shows, particularly in FIG. 5, a solution with a separating edge which is provided adjacently in the direction of conveyance or flow with a guide surface. The relationship between the separating edge and the guide surface is variable (adjustable) in EP-A-848 091, because the guide surface is fixedly attached towards the cylinder, but the separating edge is adjustable in order to enable it to adjust its xe2x80x9cimmersion depthxe2x80x9d into the stream of air/fibers.
Notice should be taken, however, that the conditions in the discharge are as sensitive as those in the working gap. On the one hand, it is necessary that the dirt be securely removed from the machine. On the other hand, the discharge should not impair the air household in the working gap per se, since the latter air household is relevant for the technological (separating) effect of the cleaning unit.
The complexity of this problem is also a function of the working width of the fiber-processing machine (of the cleaning unit). In conventional machine widths of approx. 1000 mm, suction for removing dirt has worked fine or at least satisfactorily. Larger width machines (e.g., up to 2000 mm in so-called carding machines), however, have been known to be used, and it has been proposed in EP-A-866 153 to increase the working width of the cotton card (and its tuft feeder chute) from 1000 mm to approx. 1300 to 1500 mm.
It is a principal object of the present invention to improve the air household in the discharge of dirt. It is also possible to achieve in this first aspect of the invention an improvement of the separating of dirt per se. The invention can serve to fulfill either one or the other or both of these purposes.
The invention provides in this first aspect a dirt separating device with means (e.g., an edge) for deflecting (xe2x80x9cpeeling offxe2x80x9d) dirt-loaded air from the stream of air/fibers to a dirt removal instrument or discharge, e.g., to an oblong conduit (extending over the working width). A device in accordance with the first aspect of the invention is characterized in that an air supply apparatus provides blast air to convey the dirt from the dirt removal instrument, e.g., the conduit.
The invention is provided for the particular, but non-exclusive, application in a machine which comprises a rotatable roller (cylinder or swift), with the stream of air/fibers flowing in a xe2x80x9cworking gapxe2x80x9d between the circumference of the roller and a casing encompassing the same. An edge can be provided in the casing. The selectivity of the separation is then achieved in such a way that the roller is provided with a fiber-holding clothing, while the dirt particles, which are heavier than the fibers or have a higher flow resistance, are forced by the centrifugal force radially outwardly (against the casing). The working gap usually extends over the entire axial length (over the xe2x80x9cworking widthxe2x80x9d) of the roller, and dirt is separated over the entire working width.
A machine according to the first aspect of the invention is characterized in that means are provided to introduce blast air for the conveyance of dirt into a dirt discharge.
The supply of blast air is preferably performed continuously, while the machine remains in operation. The quantity of blast air, the location of inflow, or the air speed during the inflow can be chosen in such a way that deposits in the conduit are prevented and the air household of the dirt separating device is not impaired by the blast air. The air conditions in the conduit can be chosen in such a way that the air flow in the conduit is produced merely by overpressure. In such a case, the flow is transferred at the end of the conduit to a system for further conveyance which operates by means of negative pressure.
Another object of the present invention, together with EP-A-848 091, is to provide a fiber-processing machine with a removal or separating edge, with both the fiber as well as the air being guided past the edge in a substantially predetermined direction of conveyance and dirt particles being removed from the stream of air and fibers by means of the edge. The edge is followed in the direction of flow by a flow guide surface. Means are provided in order to enable the setting of the immersion depth of the separating edge into the stream with the position of the guide surface, with respect to the stream, also being newly set when the immersion depth of the edge is adjusted.
The separating edge can be formed on an element, which is fastened to a further element that is provided with the guide surface. The fastening and the adjusting means are preferably provided in such a way that the separating edge and the guide surface maintain their respective positions during the setting.
An air introduction in accordance with EP-A-848 091 is preferably provided downstream of the guide surface.
The guide surface can be arranged as the casing of a working gap with the mutual positions of the edge and the guide surface being chosen in such a way that, downstream of the edge, the working gap need not expand at all or only marginally (e.g., not more than 0.5 mm, preferably not more than 0.3 mm). The arrangement can be such that no substantial drop in pressure is produced in the working gap downstream of the separating edge, which applies to any immersion depth of the separating edge.
A further object of the present invention is to provide a dirt separating device for the application in a stream of air/fibers in a machine of the blowroom or card room in a spinning mill comprising a separating edge and a flow guide element. The element can be arranged upstream of the edge in the direction of the flow of the machine. A discharge conduit can be formed by means of a first part of the conduit which is provided with the edge and a second part of the conduit which is provided with the flow guide element. The first and second parts of the conduit can form the discharge conduit either alone or jointly with other conduit parts, which discharge conduit is used in the machine to discharge air peeled off by the edge and material conveyed with the air transversally to the main direction of flow. The two parts can each be set individually with respect to the stream of air/fibers. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
Embodiments of the aforementioned aspects of the invention are now described below by reference to the schematic drawings.